1. Field of the Invention
This invention pertains to construction hauling equipment, and more particularly to an apparatus and method for transporting concrete cast bridge segments from the casting site to the bridge erection site.
2. Description of the Prior Art
Various equipment has been developed to transfer materials and articles between locations having different vertical and horizontal positions. For example, U.S. Pat. No. 3,103,291 shows a vehicle useful for loading and unloading airplanes, and U.S. Pat. No. 3,446,379 shows a scissors type high lift elevating mechanism. U.S. Pat. No. 4,162,873 discloses an extensible boom lift which includes a table mounted on a scissors-type lifting device and supporting a beam which is rotatable about a vertical axis. An extensible boom is supported by the rotatable beam.
The handling of precast concrete bridge segments at bridge construction sites has always presented difficult problems. The common practice is to erect two stationary cranes at great expense; the first crane is used to load the concrete segments from the casting site onto transport vehicles and the second crane is used at the construction site to unload the vehicles and mount the segments in place.
From the teachings of the existing art, there is no provision for transporting and erecting a precast concrete segmented bridge without the use of two cranes in addition to transport vehicles.
Thus a need exists for a single vehicle which will replace the function of the expensive stationary cranes at both the casting site and the bridge construction site and which will additionally perform as the transport vehicle between the two sites. Such a vehicle would have the lifting and mounting characteristics of a crane type vehicle as well as the stabilizing load characteristics of the transport vehicle. This vehicle would also be computer automated for efficient, accurate, and inexpensive operation.
In addition to the prior difficult problems of erecting precast bridge segments, there have also been difficulties in determining the weight of concrete segments during construction in order to prevent crane collapse or structure failure.
From the teachings of the existing prior art, there is no provision for weighing or accurately measuring the mass of the concrete segment during erection. Thus a need exists for a single vehicle which will function both as a crane type vehicle as well as provide a computerized digital read out of the weight of each concrete segment so that the operator who knows the design capacity of the structure under construction will not exceed this capacity by adding a concrete segment whose weight will cause the entire structure to fail.